1. Field of the Invention
This invention relates to the use of a focused beam analytic instrument designed to obtain topographical, elemental and chemical information about a material sample by impinging deflected electron and ion beams upon that sample and interpreting the mass and energy spectra of resulting emissions from that sample.
2. Description of the Related Art
At present, Focused Ion Beam instruments (FIBs), Scanning Electron Microscopes (SEMs), Secondary Ion Mass Spectrometers (SIMS) and Auger Electron Spectrometers (AES) usually operate separately. Although each of these charged particle beam instruments has its own respective domain of usefulness, there are definite advantages to integrating them into one complete instrument. FIBs, most commonly used to make connections, repairs, milling and cross-sectioning of materials on the nano-scale, can benefit from the high imaging resolution capability that SEMs provide in order to closely monitor changes made to the specimen. On the other hand, both SEMs and FIBs would benefit from being able to carry out chemical-elemental mapping analysis, the kind performed by SIMS or AES. In principle, one single instrument would be able to mill, cross-section and repair samples on the nano-scale while at the same time be able to acquire high resolution topographical, elemental and chemical maps of the samples' surface.
There are at present, dual SEM-FIB, FIB-SIMS and FIB-AES systems (L. A. Giannuzzi and F. A. Stevie, Introduction to Focused Ion Beams, Springer 2005, chapters 12, 13 and 15) however their integration is only partial. In the dual SEM-FIB or FIB-AES instruments, separate electron and ion beam columns are placed at an angle to one another. Although such an instruments can provide in situ SEM monitoring of FIB changes to a sample's surface or elemental identification, its spatial resolution is compromised by the fact that it uses a separate objective lens for each column, making it difficult to attain short working distances. On the other hand, FIB-SIMS systems typically operate with a single liquid metal source, usually Gallium, and although SIMS analysis is possible, it is preferable to have the more usual primary ion beams of Cesium and Oxygen available, due to their enhanced secondary ion yield. To make this feasible, a multi-ion beam dual FIB-SIMS instrument is required.
In the following, therefore, we describe a multi-beam charged particle instrument design, one that can simultaneously focus electrons, and a wide variety of positive and negative ion species, such as Gallium, Oxygen and Cesium ions onto the same sample. In addition, the instrument is designed to capture the spectrum of both secondary electrons and ions in parallel, in effect, combining spectroscopic SEM, FIB, SIMS and AES. The design is an advantageous extension, with a much wider range of capabilities and applications, of the present inventor's previous Spectroscopic SEM (SPS-SEM), US published application 2006/0060782A1, which is hereby incorporated fully by reference.